Studies on effect of pH on cross-linking of chitosan with sodium tripolyphosphate: A technical note

The ionotropic gelation method for formation of crosslinked chitosan particles can be easily modified from ionic cross-linking to deprotonation by adjusting the pH of TPP. Chitosan was cross-linked ionically with TPP at lower pH and by deprotonation mechanism at higher pH. The swelling behavior of cross-linked chitosan appeared to depend on the pH of TPP. The ionically cross-linked chitosan showed higher swelling ability. Thus the nature of crosslinked chitosan can be tailor made to obtain the desired properties in terms of cross-linking density, crystallinity, and hydrophilicity

Mode of action of chitosan coating on anthracnose disease control in papaya

The effect of a chitosan coating on antifungal activity and rate of respiration, chitinase and β,1-3 glucanase activities with reference to papaya variety 'Rathna' was investigated. One percent chitosan, extracted from locally available prawn waste, was selected as the effective concentration to inhibit spore germination via a series of experiments on potato dextrose agar. Rate of respiration and the concentration of CO in the internal cavity of chitosan-treated and untreated papaya were tested via gas chromatography. Chitinase and β,1-3 glucanase activities were tested in peel samples using gel diffusion and spectrophotometric assays, respectively. Complete inhibition of spore germination was observed in-vitro at treatments of 1% chitosan and above. This concentration significantly (P < 0.05) reduced both disease incidence and severity on inoculated fresh papaya. Significant (P < 0.05) decrease was observed in rate of respiration while internal CO concentration of the fruit increased (P < 0.05) with the chitosan treatment. Chitinase and β,1-3 glucanase activities of papaya variety Rathna subjected to chitosan treatment were much higher than in the untreated control. Chitosan shows antifungal activity to the anthracnose disease causing fungus and stimulates the defense response on the papaya peel by increasing the chitinase and β,1-3 glucanase activities. The antifungal activity of chitosan could be attributed to the induction of elicitation activity due to these defense enzymes. It also forms a semi-permeable coating around the fruit and extends storage life of papaya by reducing the rate of respiration and delaying ripening